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  • 1.  ECMP in OSPF

    Posted 09-12-2017 17:31



         Network1----R NY  f1-----10MIB CIR-----f1 R CHI ------Network2

                                         f2-----100MIB CIR----f2 


    Above we have  two locations  NY and Chicago, both are connected  via two CKTS of 10M and 100 M respectively.

    We are running OSPF, between the RNY and RCHI, we have also configured the same IP OSPF cost on both routers for f1/f2, and using export policy, we have now both routers in FIB i,e we have ECMP .


    Does bandwidth configured under the interface f1 and f2 i.e 10M and 100M have any bearing how traffic will be shared over these two links?  My guess is no as RNY and RCHI see both CKTS being equal  because of OSPF cost, both links have equal chance to get  picked for traffic forwarding by Load distribution algorithium.

    Am i correct to assume that?


    Thanks and have a nice day!!





  • 2.  RE: ECMP in OSPF
    Best Answer

    Posted 09-12-2017 22:12

    Yes, You are correct. Bandwidth is used in OSPF to calculate the cost of the links using the standard metric calculation fromula

    Since in your case, you have manually set the metric, it will work in a way you described.